How Does Tylenol Work?

Acetaminophen, the active ingredient in Tylenolâ„¢, is one of the most popular pain relievers in the world, selling more than 27 billion doses in 2009 alone. It can reduce fevers, eliminate aches and pains and relieve cough and cold symptoms. But how does it work? The truth is, no one knows exactly. This week, Reactions examines the theories about the popular pill.